NEET UG 2008 — Chemistry Organic Chemistry

2008mcqeasy

For the gas phase reaction, $\mathrm{PCl}_5(g) \rightleftharpoons \mathrm{PCl}_3(g)+\mathrm{Cl}_2(g)$ which of the following conditions are correct?

Official previous-year question

Held on 30 Apr 2008 · Verified 9 Jul 2026.

Options

A
$\Delta H=0$ and $\Delta S < 0$
B
$\Delta H>0$ and $\Delta S>0$
C
$\Delta H < 0$ and $\Delta S < 0$
D
$\Delta H>0$ and $\Delta S < 0$

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Solution

Key Idea : $\Delta H=\Delta E+\Delta n R T$ $\Delta n=$ number of moles of product - number of moles of reactants $\Delta G=\Delta H-T \Delta S$ For a spontaneous process $\Delta G$ must be negative. $\mathrm{PCl}_5(\mathrm{~g}) \rightleftharpoons \mathrm{PCl}_3(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g})$ In this reaction $\Delta n=2-1=1$ Thus, $\Delta H$ is positive, $i e,>0$ If $\Delta H$ is positive, then to maintain the value of $\Delta G$ negative, $\Delta S$ should be positive, $i e, \Delta S>0$ .

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NEET UG Organic Chemistry in other years

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NEET UG 2008 — Chemistry Organic Chemistry

2008mcqeasy

For the gas phase reaction, $\mathrm{PCl}_5(g) \rightleftharpoons \mathrm{PCl}_3(g)+\mathrm{Cl}_2(g)$ which of the following conditions are correct?

Official previous-year question

Held on 30 Apr 2008 · Verified 9 Jul 2026.

Options

A
$\Delta H=0$ and $\Delta S < 0$
B
$\Delta H>0$ and $\Delta S>0$
C
$\Delta H < 0$ and $\Delta S < 0$
D
$\Delta H>0$ and $\Delta S < 0$

Did you get this right?

Solution

Your note

NEET UG Organic Chemistry in other years

Keep practicing Organic Chemistry

Work through every NEET UG Organic Chemistry PYQ, year by year.

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NEET UG 2008 — Chemistry Organic Chemistry

Options

Did you get this right?

Solution

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NEET UG Organic Chemistry in other years

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Other Chemistry topics for NEET UG

Physical Chemistry

Inorganic Chemistry

Keep practicing Organic Chemistry

NEET UG 2008 — Chemistry Organic Chemistry

Options

Did you get this right?

Solution

Your note

NEET UG Organic Chemistry in other years

More NEET UG Organic Chemistry questions

Other Chemistry topics for NEET UG

Physical Chemistry

Inorganic Chemistry

Keep practicing Organic Chemistry